PROJECT SUMMARY Overweight/obesity is strongly linked to mortality from multiple chronic diseases, including obesity-related cancers. For health disparity-facing populations, including racial/ethnic minority and/or low income individuals, who have both high prevalence of obesity and cancer, interventions promoting behavioral change for nutrition, physical activity, and weight are a national health priority. A growing knowledge base documents the efficacy of community health worker supported interventions for improving behavioral change due, at least in part, to their unique insights into how an intervention should be adapted to social and environmental contexts. While there has been a rapid expansion in the use of digital technologies for delivering health interventions, there has been little study of the potential use of these technologies in the U.S. by non-professional health workers, including community health workers. Yet, it is not yet clear if digital technologies alone are efficacious for weight loss, particularly among health disparity-facing populations, or if a more intense intervention consisting of a combination of community health workers plus digital technologies will be needed to successfully promote weight loss among health disparity-facing populations. In the proposed research study, we will target weight management among obese residents of Boston's public housing developments who are low-income and predominately from racial/ethnic minority groups. This R01 proposal seeks to examine the efficacy of an intervention approach that combines mHealth technology plus website-driven behavioral counseling from community health workers. Our hypothesis is that in a 12-month cluster-randomized trial (n=504) comparing 3 public housing developments (n=168 participants) who receive community health worker motivational interviewing behavioral counseling plus mHealth self-monitoring/text message feedback (mHealth+CHW), versus 3 developments (n=168) who receive the mHealth self-monitoring/text message feedback only (mHealth only), versus 3 developments (n=168) who receive assessment only (control group), both mHealth+CHW and mHealth only will outperform assessment only control and mHealth+CHW will outperform mHealth only in terms of weight loss at 12 months. For secondary outcomes, we will examine intervention effects on diet and physical activity behaviors. We will also examine mediating effects of Social Cognitive Theory constructs and moderating effects of participant characteristics and social contextual variables on the effect of the intervention. Finally, we will conduct a cost-effectiveness analysis. Our results will enable a better understanding of efficacious approaches to weight management among health disparity-facing populations, which may be applied to other modifiable cancer risk behaviors and be extended into the larger federal network of public housing administrations.